Generally, a conventional front-wheel drive vehicle has two drive shafts, each of which interconnects a transmission and a front wheel such that the driving force outputted from the transmission is transferred to the front wheels. Typically, the left wheel drive shaft is directly connected to a differential gear, and the right wheel drive shaft is connected to the differential gear through an inner-shaft.
The inner-shaft is mounted to the vehicle body by a supporting means in order to interconnect the differential gear and the right wheel drive shaft such that a balance between the left wheel, driven by the left wheel drive shaft, and the right wheel, driven by the right drive shaft, can be achieved. In order to prevent moisture or dust from infiltrating into the inner-shaft bearing, typically a complex quadruple seal structure is provided.
However, such a seal structure is complicated and takes a relatively long time to assemble. Furthermore, when the inner-shaft bearing emits heat during the driving of the inner-shaft, the pressure inside of the bracket sealed with the first packing and the second packing is increased such that the first packing and the second packing expand and the lubricating oil can leak out thereof.